There is proposed a vehicle security system that is designed to prevent an unauthorized use of a stolen vehicle by disabling the use of the vehicle or deter a robbery of a vehicle by openly disclosing that a vehicle is mounted with the function of disabling the use of the stolen vehicle.
This security system is equipped with an immobilizer function that is to be remotely activated. When a vehicle mounted with this system is stolen, the following takes place. A regular owner of the stolen vehicle reports the robbery of the vehicle to a base station. The base station thereby transmits to the stolen vehicle an instruction signal for activating the immobilizer function using wireless communications. The vehicle that has received the instruction signal activates the immobilizer function so as to prohibit the engine from being started. Here, when the engine is running, the security system forcibly stops the running engine and then prohibits a re-starting of the engine, or, in view of safety, prohibits the re-starting of the engine after the running engine once stops (e.g., refer to Patent document 1).
Patent document 1: JP 2003-146185 A
In the above security system, releasing the activated immobilizer function after the stolen vehicle is sought out is performed so as to re-start the engine only by the following: a regular key capable of releasing the immobilizer function; or transmission of an instruction signal, which requests releasing of the immobilizer function, from the base station. Here, the regular key transmits a unique ID code so as to release the immobilizer function.
Therefore, when the vehicle is stolen along with the regular key, the robber of the vehicle can release the immobilizer function, possibly decreasing the meaning of the immobilizer function. Further, when the instruction signal to release the function is transmitted from the base station but the stolen vehicle is under a situation where the vehicle cannot receive the transmitted instruction signal, the immobilizer function cannot be released. This incapability of receiving the signal by the vehicle occurs: when the vehicle is parked at a place such as a basement or a tunnel; where no radio waves reach; or when the receiver mounted in the vehicle for the instruction signal is broken.